Many means are known for authenticating a sheet, by giving it recognizable characteristics during the manufacture of a sheet. For example, a watermark makes it possible to modify a sheet's local transparency. Similarly, inserting materials, such as fibers or bands, into the paper should allow the sheets formed with this paper to be made forgery-proof.
However, these techniques are very costly and are reproduced, more or less closely, by counterfeiters.
There are techniques for memorizing physical characteristics of a sheet, for example the shape of fibers in a given portion of the sheet. However, recognition of the sheet on the basis of a new analysis is very sensitive to variations in the analysis angle, particularly of the image sensor, and in the end can only be used in a laboratory.